1. Field of the Invention
This invention relates to an automatic bar feeder device, especially for CMC lathes, which is to be used in a magazine bar feed, and comprising a device for transferring a bar to be machined from a hopper on a bench, and a device for advancing said bar into the lathe, this advancing device containing a short advance module equipped with a flag, and a long advance module equipped with a thrustor.
Feeder devices, comprising a bar loading device, a device for their advance, and a centering device, are used in apparatuses currently called "magazine bar feeds" of which different types are on the market.
The task of these apparatuses is to automatically feed especially automatic or CNC lathes; automatic feed sensibly increases the yield of the latter and substantially reduces the unit costs of the pieces machined on the lathes of this kind.
2. Description of the Prior Art
Known magazine bar feeds generally have the shape as shown, in a very schematical manner, in attached FIGS. 1A and 1B (side and front view, respectively) : There is a frame 10, a cradle 11 within the frame, a bench 12 shaped as a very open V, said cradle being optionally covered by a hood 13, and an inclined plane hopper 14 whose inclination can be adjusted by the device 15. A bar 17 which is laid down on the bench 12 has beforehand been transferred from the hopper 14 on said bench. The bar is to be machined on a lathe, represented by a mandrel 19 and a headstock 9, after having been introduced in this headstock by an advance device 18.
The functional principle of known feeder devices can easily be understand from FIG. 2A to 2F which show a lateral view of such a device:
In FIG. 2A, the bars to be machined 17A, 17B, 17C etc. are placed or stored on the hopper 14 and blocked there by a shoulder 14A. The bench 12 and a set of grippers 16 (from which only one is shown) connected thereto are in a defined position which corresponds to that shown in FIG. 2D in such a manner that, when a bar 17A is placed on the V, its axis and the axis of the headstock of the lathe would have the same support.
In a first step, the unit 12, 16 rises, the grippers lift the first bar 17A according to the vertical arrow (FIG. 2B) until said bar swings over the shoulder 14A of the hopper 14 (FIG. 2C) and falls all of a sudden into the V of the cradle (FIG. 2D, showing the position of the bench 12 where the axis of the bar 17A and that of the lathe headstock have the same support). During these operations, the next bar 17B is held back by the rear flank of the gripper 16.
In a second step (not shown), a short thrustor called flag (first module of an advance or thrusting device) pushes the bar to be machined into the lathe headstock.
In a third step, the unit 12, 16 goes down according to the arrow (FIG. 2E) until it takes its original or starting position of FIG. 2A (FIG. 2F). Simultaneously, the next bar 17B which is no longer held back by the gripper 16, rolls on the inclined plane of the hopper 14 (see arrow in FIG. 2F) and comes to rest against the shoulder 14A which blocks the travel.
Finally, in a fourth step, the flag goes back and gives room for a long thrustor (second element of the advance device) whose function is to take care of the advance or the succeeding advances of the bar until its complete machining, according to the strokes shown in FIGS. 3A to 3D: The material advance (namely that of the bar 17A) is effected by the action of the thrustor 18, the jaws of the mandrel 19 being open (FIG. 3A). The bar is then clamped (FIG. 3B), and the machining is undertaken (FIG. 3C) When the machining is finished, cutting off is made (FIG. 3D), and a new machining cycle can be started, for example on the same bar 17A; this is to say that the mandrel jaws open, the thrustor 18 is advanced and pushes the bar 17A over a defined distance, etc.
These known apparatuses and devices have several kinds of disadvantages.
First, the loading operations come about brutally since the apparatus is subject to two succeeding shocks during each of these operations.
A first shock comes from the fall of the bar 17 to be machined (17A, 17B, etc. in FIGS. 2A to 2F) into the V of the bench down from the grippers (FIG. 2C).
A second shock occurs from the fall of the next bar 17B against the stop shoulder 14A of the hopper (see FIGS. 2E and 2F), this bar being itself under the push of the higher bars 17C, 17D, etc. (FIG. 2F).
As a rough indication, the weight of a sole bar having a diameter of 80 mm and a length of 1,200 mm is about 47 kg.
It can easily be understood that these shocks, as to their effects, will be damaging to the magazine bar feed itself as well as to the lathe which it feeds. More particularly, the shocks provoke an increasing misalignment between the magazine bar feed and the headstock of the lathe at such an extent that, from a certain moment, the bars will hit the headstock which will thus cause serious damages (especially destroying the bearings of the headstock, resulting in worse machining precision and reduction of the lifetime of the lathe).
Another serious drawback is the absence of any apparatus polyvalence since the known devices only allow the loading of bars and not their unloading. However, in some cases, for example when bars should be machined at one end, it would be advantageous to unload these bars after machining by means of the magazine bar feed.
In certain known magazine bar feeds, the advance device comprises two parallel disposed cylinders which are next but distant to each other, a first cylinder coacting with the short thrustor (flag) and a second one with the long thrustor. The loading comprises three steps: first, the introduction of the bar by means of the flag, driven by the first cylinder, and the retreat of said flag; then, a lateral displacement of the two cylinders by means of a horizontally movable carriage, in order to place the long thrustor in the headstock axis, namely the bar axis; and finally the advance of the long thrustor, driven by the second cylinder. Other known magazine bar feeds are equipped with two thrusters, a short and a long one, vertically superimposed and mounted on a vertically movable carriage. In still other known magazine bar feeds, already more improved, the two thrustors are mounted on a seesaw, the short thrustor or flag making the first introduction and the long thrustor pushing the bar into the headstock for machining, these two thrusters being driven by the same cylinder but the seesaw remaining driven by a separate cylinder. All these devices would be improved when they were less complicated, more purposeful and less expensive.
Regarding known centering devices, their handling is not easy, and the centering operations are carried out neither quickly nor purposefully.